1. Field of the Invention
The present invention refers to a system for vacuum-refeeding sheets, in particular corrugated board sheets, to be used, for example, in printing and die cutting machines in order to prepare packaging boxes.
2. Description of Rrior Art
Systems of this type are known, in which there is a sheet-transporting device, that connects the printing station to the die cutting station in a rotary printing machine. This sheet-transporting device allows conveying sheets by vacuum, in particular corrugated board sheets or similar sheets, by applying an upward-directed suction force generated by a fan placed inside an upper hood of the system. A horizontal sheet displacement is therefore obtained, where the sheets are grasped by two rubber rollers and then pass, pushed by two belts with small blocks, on idle rollers in contact with the upper face thereof without having to make these sheets pass on cylindric rollers that will make the lower face of the sheets dirty, as soon as a sheet has been printed on by the upstream printing station.
The above-described device has the problem that it has been necessary to have sheets available whose width is greater than the distance between the two belts, so that the belts could push the sheets through the small blocks. Therefore the belts must have been transversally adjusted at every work-change, with obvious operating problems. Furthermore, the belts reduce the available space under the sheets, occupied in this case by a small-sized drying machine, that thereby guarantees a less effective drying operation.